The present invention relates to analytical equipment for performing electrochemical assays on microbial samples. In particular, the present invention relates to electrodes for use in such analytical equipment.
Accurate and rapid determination of microbial activity is essential in many areas, including pollution control; quality assurance in the food, drink and drugs industries; and clinical analysis of bodily fluids and other medical samples.
For a long time, the standard method for the enumeration of bacteria has been an agar plate count. This method has many disadvantages, especially the time needed to obtain results. Even with the fastest growth, 18 hours is needed for visible colony formation, and then there is the task of counting the colonies.
There have been proposals to employ bioelectrochemical cells or fuel cells for assaying or microbiological samples. For example, amperometric determination of viable cell numbers based on sensing microbial respiration is described in Appl Microbiol Biotechnol (1981) 12, 97; the use of a microbial fuel cell for the rapid enumeration of bacteria is described in Appl Microbiol Biotechnol (1988) 28, 26; and an investigation of a simple amperometric electrode system to rapidly quantify and detect bacteria is described in J Appl Bacteriol (1989) 66, 49. Further aspects of amperometric bioassay systems are described in EP 190470 and 238322, and GB 2181451 and 2181558, among other examples. Some of these systems employ a filter to capture microbial cells at the electrodes, after which the determination is effected.